Snap action switch



Sept. 6, 1966 s. H. SCHWARTZ 3,270,573

SNAP ACTION SWI TCH Filed March 29, 1963 United States Patent '0Illinois Filed Mar. 29, 1963, Ser. No. 269,113 9 Claims. (Cl. 74-97 Thisinvention relates to snap action motion translation devices whereby therelatively slow movement of a first member will be transmitted at agiven instant to a second member with a rapid and powerful stroke.

Snap action mechanisms have been in use for a number of years and havefound particular utility in electrical switches.

The usual type of snap action switch mechanism comprises a frame havinga short snap blade and an elongated snap lever pivotally mounted aboutthe same axis on the frame. A compression spring interconnects the freeend of the snap blade with the free end of the snap lever so that whenthe spring connection point on the snap blade is moved past the plane ofthe snap lever the lever will be urged in a direction opposite that ofthe blade with a rapid snap motion. If the mechanism is incorporated inan electrical switch the snap lever ordinarily constitutes the movablecontact of the switch and is engageable in one or the other of itsextreme positions with a stationary contact. Some times of course thesnap lever engages different contacts at each end of its pivotal strokein a double pole switch.

Oftentimes, for the sake of simplicity and inexpensive construction, thesnap lever and snap blade are merely formed from a flexible materialsuch as a thin metal and the ends thereof are rigidly secured to theframe support so that the lever and blade simply move in one directionor the other as the operator moves the blade to one side or the other ofthe lever but the result is the same as if their ends were actuallypivoted on the supporting frame.

A significant drawback in such snap action mechanisms resides in thefact that very little force is exerted by the snap lever at that instantwhen the snap blade has just moved past the plane of the snap lever. Infact, little force is exerted by the lever until the free ends of thesnap blade and snap lever have been moved apart a substantial distance.That is, in a conventional snap mechanism the main snap lever exerts azero force at the beginning of its stroke which will build up as thelever moves following a sine curve approximately. This characteristic isnot particularly disadvantageous when a snap action mechanism isemployed in an electrical switch.

However, it has now been found desirable to employ snap actionmechanisms in other environments for the purpose of carrying aconsiderable work load. For instance, it has been proposed that amechanism of this type be employed to shift a motor drive belt back andforth on a two-speed sheave in an automatic dryer. Such an applicationrequires a quick motion and an immediate application of a substantialforce which must, of course, persist throughout the stroke of the snaplever.

The motion translation device which I have devised is effective totranslate a slow pivotal stroke of the snap blade (which I hereafterrefer to as an actuating lever) into a rapid pivotal snap lever (mainlever) stroke. In addition, the motion translation device which I havedevised has a very considerable snap lever power output because I haveradically improved the leverage advantage between the snap blade and thesnap lever.

The device which will hereafter be described with more particularityincludes a snap blade or actuating lever and a snap lever or main leveras does the usual type of snap action mechanism. These members are eachpivotally mounted on a frame, preferably about the same axis. Anadditional toggle element however is added to the mechanism and thistoggle is pivotally mounted on the free end of the main lever. Acompression spring interconnects the free end of the actuating leverwith the toggle element so that when the spring connection point on theactuating lever is moved on one side or the other of the plane of thetoggle element the toggle element will first be pivoted relative to themain lever and the main lever will then be pivoted by the action of thespring on the toggle element with respect to the frame.

The primary advantage achieved by construction of a device of thischaracter is that the toggle element is first pivoted relative to themain lever without any substantial resistance to its movement and whenthe toggle element has been thus pivoted there is a considerableleverage advantage between the free end of the actuating lever and thefree end of the toggle element. It is not until the actuating lever andthe toggle element are thus disposed that any movement of the main leveris effected. Obviously, when the main lever does begin to move there isa considerable spring load applied to it to effect such movement and thepower output of the mechanism is considerable.

I have also designed the mechanism so that, in combination with atemperature sensitive power unit, it will be thermostatically actuable.

In view of the foregoing, it is a principal object of my invention toprovide an improved motion translation device in which snap actuation ofa lever can be effected and in which considerable force can be appliedto the lever throughout its pivotal stroke.

Another object of my invention resides in the provision of a snap actionmotion translation mechanism in which the usual over-center springacquires a considerable leverage advantage before effecting pivotalmovement of the main lever.

Another object of my invention as directed to the provision of athermostatically actuable snap action mechanism of the character abovedescribed.

These and other objects, features and advantages of my invention willappear from time to time as the following specification proceeds andwith reference to the accompanying drawings, wherein:

FIGURE 1 is an exploded view of a thermostatically actuable motiontranslation device constructed in accordance with the principles of myinvention;

FIGURE 2 is a diagrammatic representation of a motion translation deviceshown in a first position;

FIGURE 3 is a diagrammatic representation of the device illustrated inFIGURE 2 but showing the mechanism in a second position; and

FIGURE 4 is a diagrammatic representation of a different form of amotion translation device constructed in accordance with the principlesof my invention.

Referring initially to FIGURE 1, a frame 10 is generally U-shaped inconfiguration and has a base wall 11 centrally apertured at 12 and apair of spaced vertically extending legs 13 and #14. The base wall 11rests on a diametrically enlarged collar 15 of a temperature sensitivepower unit 16 which also has a temperature sensing portion 17, a powermember guide '18, and a power member 19 mounted for axial movementwithin the guide 18 in a manner well understood by those skilled in thisart.

The temperature sensitive power unit =16 is of the wellknown solid sfilltype having a crystalline wax or a similar temperature sensitivesubstance within the temperature sensing portion 17 thereof and having adiaphragm extending across the interior of the unit where the collar '15is so that thermal expansion of the wax with-in the sensing portion 17will be transmitted through the diaphragm to the power member 19abutting the diaphragm to effect extensible movement of the power member'19 relative to the guide 18.

Portions of the temperature sensitive power unit 16 are peened over thebase wall 11 of the frame to rigidly secure the frame to the power unit.

An actuating lever 20 is somewhat T-shaped in configuration having apair of outwardly extending wings 21 extending therefrom and having anose 22 extending from the opposite end thereof. The lever is fiat andhas a pair of projections 23 extending upwardly from the upper surfacethereof.

The actuating lever 20 is pivotally mounted on the legs 13, 14 of theU-sh-aped frame 10 by the wings 21 which extend through coaxiallyaligned apertures 24 formed within reariwardly extending tabs 25 which,in turn, are formed integrally with the legs 13, 14 of the frame 10.

It will be observed that the under-surface of the actuating lever 20rests on the outer free end of the power member 19 and that it is biasedinto engagement with the power member by a compression spring 26 whichis interposed between the lever 20 and a pair of spring retainingfingers 27. The fingers 27 are formed integrally with the frame 10 andhave downturned nibs 28 which assure that the spring 26 will be centeredin its proper position. The upstanding nibs 23 on the lever 20 serve thesame purpose for the lower end of the spring 26.

It will be observed that the wings 21 are of such a length that theyextend completely through the tabs 25 and for a short distance past theouter surfaces thereof to provide a pivot for the main lever. The mainlever 30 is also U-shaped in con-figuration and has an end Wall 3-1 anda pair of integral rearwardly extending spaced lugs 32, 33 which areapertures as at 34. The apertures 34 in the legs 32, 33 receive theoutwardly extending end portions of the wings 21 so that the main lever30 is pivotally mounted on the Wings 21 and hence about the same pivotalaxis as the actuating lever 20.

A depending tab 35 is formed integrally with and extends from the endwall 31 of the main lever 30 and has an aperture 36 formed therein whichserves as a connection point for any element which is to be operated bypivotal movement of the lever '30.

A T-shaped toggle 40 is fiat and has a pair of outwardly extending wings41 which are received within arcuately shaped apertures 42 formedwith-in the legs 32, 33 of the main lever 30. The toggle has forwardlyand rearwardly extending noses 43 and 44 formed integrally therewith andthe nose 43 is loosely fitted within an aperture 45 formed in the endwall 31 of the main lever 30 to center the toggle between the legs 32,33 of the main lever. A knife edge bearing surface 46 is formed on thetoggle element on each side of the nose 43 and is cooperable with a V-groove formed on the inner face of the end Wall 31 to pivotally mountthe toggle element relative to the main lever 30.

A compression spring 47 interconnects the toggle 40 and the actuatinglever 20 and is coiled about the noses 44 and 22 on these two elementsrespectively.

A plurality of nibs 48 are tormed integrally with and extend outwardlyfrom the legs 13, 314 of the U-shaped frame 10 and are positioned in thepath of a pivotal movement of the main lever 30 to provide a means forlimiting the degree of pivotal movement of that lever.

'It will be observed from a consideration of FIGURE 1 in connection withthe diagrammatic representations of FIGURES 2 and 3 that when the springconnection point A of the actuating lever 20 is moved above the plane oftoggle in that figure, the toggle element will be snapped rapidly fromthe full line position to the broken line position shown therein. Thereis of course no substantial resistance to such pivotal movement of thetoggle element relative to the main lever 30.

It will be understood of course that the broken line position of themechanism shown in FIGURE 2 is not an at-rest position and has beenillustrated for clarity of description only. As soon as the toggleelement has been moved to the broken line position of FIGURE 2 thespring will then act through the toggle element to pivot the main lever30 relative to the frame 10. It will be observed however that the spring4 7 has a considerable leverage advantage when such pivotal movement ofthe lever 30 is in'itated. It is primarily this feature of applicantsdevice which constitutes such improvement over the prior known motiontranslation mechanisms.

Conversely, if the various parts of the mechanism are initially in theposition shown in FIGURE 3, then movement of the spring connection pointA above the plane of the toggle element will act first to pivot thetoggle element upiwardly sothat it lies above the plane of the snaplever and then snap actuation of the lever itself will be effected.

The embodiment of the invention shown diagrammatically in FIGURE 4 hasbeen included in this disclosure for the purpose of illustrating thatthe actuating element 20 need not be positioned so as to face in thesame direction as the 'main lever 30 with respect to the frame 10. Onthe contrary, the lever might Iface rearwardly of the frame 10 but theprinciple of operation is, of course, substantially the same as thatwhich has been heretofore described.

It will be understood that these embodiments of my invention have beenillustrated and described for illustrative purposes only and variousmodifications and varia tions in my invention may be effected withoutdeparting from the spirit and scope of the novel concepts there-0t.

I claim as my invention:

1. A motion translation device comprising:

a frame,

an actuating lever and a main lever both pivotally connected to saidframe and having free ends extending outwardly from said frame,

a toggle pivotally connected to the free end of said main lever andhaving a free end positionable on each side of a straight lineintersecting the pivotal axes of said main lever and toggle,

means limiting the degree of pivotal movement of said toggle relative tosaid main lever and said main lever relative to said frame,

resilient means interconnecting the "free ends of said toggle and saidactuating lever,

and means for positioning the free end of said actuating lever on eachside of a line intersecting the spring connection point on said toggleand the pivotal axis of the toggle irrespective of the pivoted positionof said toggle and irrespective of the pivoted position of said mainlever.

2. A motion translation device comprising:

a frame,

a flat actuating lever and a flat main lever both pivotally connected tosaid frame and having free ends extending outwardly from said frame,

a flat toggle pivotally connected to the free end of said main leverand'h-aving a free end positionable on each side of the plane of saidmain lever,

means limiting the degree of pivotal movement of said toggle relative tosaid main lever and of said main lever relative to said frame,

a compression spring interconnecting the free ends of said toggle andsaid actuating lever,

and means for positioning the free end of said actuating lever on eachside of the plane of said toggle irrespective of the pivoted position ofsaid main lever.

3. A motion translation device comprising:

a vertically extending frame,

an actuating lever and a main lever pivotally connected to said frameand having free ends extending outwardly from said frame on the sameside thereof,

a toggle pivotally connected to the free end of said main lever andhaving a free end positionable on each side of a straight lineintersecting the pivotal axes of said main lever and toggle,

means limiting the degree of pivotal movement of said toggle relative tosaid main lever and said main lever relative to said frame,

a compression spring interconnecting the free ends of said toggle andsaid actuating lever, and means for positioning the free end of saidactuating lever on each side of a line intersecting the springconnection point on said toggle and the pivotal axis thereofirrespective of the pivoted position of said main lever.

4. A motion translation device constructed in accordance with claim 1wherein said levers are pivoted on said frame about the same axis.

5. A motion translation device comprising:

a frame,

an actuating lever pivotally connected to said frame and 'having a freeend extending outwardly therefrom,

a U-shaped main lever having a pair of spaced legs pivotally connectedto said frame about the pivotal axis of said actuating lever and havinga free end extending outwardly therefrom,

a toggle pivotally connected to the free end of said main lever andhaving a free end disposed between the said legs of said main lever andpositionable on each side of a straight line intersecting the pivotalaxes of said main lever and said toggle,

means limiting the degree of pivotal movement of said toggle relative tosaid main lever and said main lever relative to said frame,

a compression spring interconnecting the free ends of said toggle andsaid actuating lever,

and means for positioning the free end of said actuating lever on eachside of a line intersecting the spring connection point on said toggleand the pivotal axis of the toggle irrespective of the pivoted positionof said main lever.

6. A motion translation device constructed in accordance with claim 5wherein said actuating lever is also positioned between the said legs ofsaid main lever and extends outwardly from said frame in the samegeneral direction as said main lever.

7. A motion translation device constructed in accordance with claim 5wherein the means for limiting the degree of pivotal movement of saidtoggle relative to said main lever comprises at least one wing extendingoutwardly from said toggle and an associated arcuately shapedwing-receiving aperture formed in a leg of said U-shaped main leve-r.

'8. A motion translation device constructed in accordance with claim 5wherein the means for limiting the degree of pivotal movement of saidmain lever relative to said frame comprises a pair of projections formedintegrally with said 'frame and positioned in the path of pivotalmovement of at least one leg of said main lever.

'9. A motion translation device constructed in accordance with claim '5wherein the means for limiting the degree of pivotal movement of saidtoggle relative to said main lever comprises at least one wing formedintegrally with and extending from said toggle and at least onecooperating arcuately shaped aperture formed within one leg of said mainlever for receiving said toggle and wherein the means for limiting thedegree of pivotal movement of said main lever relative to said framecomprises a pair of nibs formed integrally with and extending from saidframe in the path of pivotal movement of at least one 'leg of said mainlever.

References Cited by the Examiner UNITED STATES PATENTS 1,375,247 4/ 1921Behrens 74-97 2,241,981 5/1941 Cerny 7497 X 2,334,007 1'1/1943- Hutt20067 2,614,186 10/ 1952 Sutton et a1 7497 X 2,761,029 8/1956 Peabody7497 X 3,001,401 9/1961 Vernet et al. 733-58 3,112,382 11/1963 Baker200- X LOUIS R. PRINCE, Primary Examiner. D. M. YASICH, AssistantExaminer.

1. MOTION TRANSLATION DEVICE COMPRISING: A FRAME, AN ACTUATING LEVER ANDA MAIN LEVER BOTH PIVOTALLY CONNECTED TO SAID FRAME AND HAVING FREE ENDSEXTENDING OUTWARDLY FROM SAID FRAME, A TOGGLE PIVOTALLY CONNECTED TO THEFREE END OF SAID MAIN LEVER AND HAVING A FREE END POSITIONABLE ON EACHSIDE OF A STRAIGHT LINE INTERSECTING THE PIVOTAL AXES OF SAID MAIN LEVERAND TOGGLE, MEANS LIMITING THE DEGREE OF PIVOTAL MOVEMENT OF SAID TOGGLERELATIVE TO SAID MAIN LEVER AND SAID MAIN LEVER RELATIVE TO SAID FRAME,RESILIENT MEANS INTERCONNECTING THE FREE ENDS OF SAID TOGGLE AND SAIDACTUATING LEVER, AND MEANS FOR POSITIONING THE FREE END OF SAIDACTUATING LEVER ON EACH SIDE OF A LINE INTERSECTING THE SPRINGCONNECTION POINT ON SAID TOGGLE AND THE PIVOTAL AXIS OF THE TOGGLEIRRESPECTIVE OF THE PIVOTED POSITION OF SAID TOGGLE AND IRRESPECTIVE OFTHE PIVOTED POSITION OF SAID MAIN LEVER.